I have obstructive sleep apnoea, and though it's not something I tell many people, it does give me the unusual opportunity to be able to test CPAP respiratory machines. Sleep apnoea is a huge part of my life, I rely on "my machine" and know that without it my next day will be a sleepy torture.

(Credit: Fisher & Paykel)

Buying a CPAP machine is an expensive endeavour with real, life-changing benefits. My first machine was a no-frills model, offering a constant pressure and no costly "luxury" items, like humidification and heating. But are these features really just comfort features or should you consider spending the extra money?

When I was recently asked by Fisher & Paykel to take a look at its new ICON range I made it clear that I wouldn't be reviewing the product, per se. A mobile phone reviewer with sleep apnoea is far from an expert in this field and I certainly don't profess to having any specific medical advice to impart. But this experience did have me revisiting my own original CPAP purchase and wondering if I would have made the same choice then knowing what I know now.

What to look for in a CPAP machine

Regardless of whether you buy a ResMed, a Respironics or a Fisher & Paykel-branded machine, you will have your prescribed airflow delivered. In my experience there isn't much difference between machines when it comes to pushing the air up the coiled tubing. What does set these machines apart are elements that I had wrongly assumed were "luxury" items; attachments like heated tubing and a humidifier and features like automatic pressure adjustment. When you consider how important and how fragile our sleep can be, these so-called luxuries can soon seem like essentials.

Humidification

When I bought my first CPAP machine it was my understanding that humidification was something that could make you more comfortable while you slept, something to make the air slightly warmer so you didn't wake up feeling "wind-blown". I didn't, at the time, understand that my choosing not to pay for the humidifier attachment may have been the reason I was getting a cold three or four times a year.

According to the clinicians at Fisher & Paykel, "up to 75 per cent of CPAP users (without a heater humidifier) complain of upper airway dryness and congestion". During this road test I found my persistent sinus congestion somewhat relieved. I then switched back to my older machine without humidification for a week to compare results, and found there really is a significant difference in how it feels to use these machines. Using a humidifier can be a little unusual for the first few nights, but I now believe it's an essential part of my treatment.

The downside to humidification can be condensation. When the warm air leaves the CPAP machine and hits colder air in the tubing before the mask condensation may form, you can sometimes wake up with a small pool of water in your mask. One of the newer features of CPAP treatments is heated tubing, which should deter condensation by maintaining a constant temperature along the tube to your mask. A heated tube also makes breathing much more comfortable, especially during the colder months of winter.

This diagram shows how condensation is formed, and deterred, in CPAP tubing.
(Credit: Fisher & Paykel)

All CPAP machines have humidification options, the Fisher & Paykel range have built-in humidifiers in all machines, ResMed has its Humidair attachment and patients using REMstar machines can choose a REMstar humidifier.

Auto vs. constant pressure

Automatically adjusting airflow was another feature I chose not to pay extra for in my first machine, which I now regret in hindsight. Though, unlike humidification, automatically adjusting airflow is definitely not a feature everyone will need. It was explained to me that automatically adjusting air pressure (or APAP) could help make treatment more comfortable for patients who have difficulty complying with their treatment due to discomfort. This was never an issue for me, I took to CPAP like a very sleepy duck to water, but this didn't mean that I wouldn't have benefited from an APAP machine.

With an Auto machine you have it set to a range of acceptable pressure, usually with your prescribed pressure somewhere in the middle, and the machine will determine which pressure you need each night based on your breathing. Generally, Auto machines are appropriate for people with a prescription of 10cmH20 or higher, anyone who is likely to change weight after a planned surgery or anyone who is having difficulty acclimatising to the high air pressure the machine is required to deliver.

After monitoring my results using the ICON machine over a month I could see, among many other interesting bits of data, that each night the machine delivered a different median air pressure and the instances of apnoea and hypopneas recorded varied as well within a safe range. No two nights of sleep are ever the same, and having the machine accommodate those fluctuations seems like a good idea to me.

That said, an Auto machine will be more expensive, twice the price of a basic CPAP machine in some instances, so this is one feature you will have to experience for yourself. Before committing to the purchase of a machine, trial both CPAP and APAP systems, and make sure you speak to the sleep specialist you have been consulting for their opinion.

Algorithms!

If you compare the top of the line machines across the range from ResMed, Fisher & Paykel, Respironics and REMstar they all include a number of proprietary comfort algorithms. I had a chance to try SensAwake, Fisher & Paykel's mathemagic algorithm which detects when you are in a lighter sleep, based on inconsistencies in your breathing patterns, and lowers the pressure delivered by the machine so as to not disturb you. The best example of this is in the morning; as you begin to wake your breathing will change and become more erratic, and the machine will lower the pressure of the airflow so that it doesn't wake you unnaturally.

I alternated between nights with SensAwake turned on and others with it deactivated. Looking back at the data produced by the machine, there appears to be indications of more restless sleep when I wasn't using SensAwake, characterised by patches of irregular breathing throughout the night. In all honesty, I can't say I have noticed the effect of SensAwake as I've slept, but the data seems to suggest a more relaxed sleep on the nights when it was turned on.

Fisher & Paykel also uses a different system called ThermoSmart for making sure condensation in your mask is kept to a minimum. Official Fisher & Paykel documentation tells us that ThermoSmart is a system in which the machine's heated tube and humidification algorithm work together to "provide optimal humidification without condensation".

The effect of ThermoSmart is more obvious than SensAwake. I have used humidifiers in the past and recall numerous occasions when I woke up with water in my mask in the morning. During my month with the ICON this didn't happen at all, nor did I wake up feeling any discomfort in my sinuses.

Other CPAP machine manufacturers have similar concepts under different names. The new ResMed S9 has Easy-Breathe Expiratory Pressure Relief to control airflow and Climate Control to minimise condensation, for example.

Beyond the road test

If I were buying my first machine again I'd like someone to have explained the benefits of attaching a humidifier to my CPAP machine. The built-in humidifier in the ICON machine matched with its heated tubing provided a great increase in comfort over the system I had been using previously. Comfort may not seem like it's worth paying for when you're talking about an extra AU$1000 or more, but we strongly recommend you consider spending extra if you can afford to.

Assessing the importance of automatic pressure versus constant pressure, and determining the effect of the built-in algorithms is more difficult to gauge, but where possible we suggest you try as many machines as possible before making a purchase. We'd be surprised if you could find much difference between the algorithms of the various brands of machines available, but we did see some evidence that features like SensAwake can make you more comfortable while you sleep.

About the author

Joe capitalises on a life-long love of blinking lights and upbeat MIDI soundtracks covering the latest developments in smartphones and tablet computers. When not ruining his eyesight staring at small screens, Joe ruins his eyesight playing video games and watching movies.
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